The reduction of pollutant gases in the atmosphere, responsible for global warming, associated with global oil reserves reduction pushed many countries to search for an alternative solution of both problems. Brazil, as one of the pioneers in the use of alternative fuels, mostly due to the development of the ethanol technology, has started an ambitious program regarding Biodiesel. Biodiesel is an organic fuel that can be obtained through different processes, being the transesterification of oil the most commonly used. The oil used in the process can be from animal or vegetal origin or a mixture of both. Since Brazil has one of the biggest cultivable areas in the world, it is evident that the success in the domain of this technology depends mostly of political will. The law 11.097, of Jan. 13, 2005, establishes a mandatory minimum mixture percentile of biodiesel in the diesel oil to be commercialized to the public all over the country. This percentile will be of 5% after eight years after the law publication date, with an intermediary value of 2% three years after the publication. In the future the tendency is to an increase in those percentiles as a function of the increase of global warming and due to global political conjuncture regarding natural oil sources. Based on the presented situation it becomes evident the need for a method to determine mixture percentiles of biodiesel in diesel oil for manufacture control, quality control, law enforcement and for engine managing and control.
The previous art related regards to the mixture measurement of alcohol-gasoline mixture measurements using near infrared light (“Near Infrared” or NIR—0.65 a 2.5 μm).
International patent WO90/03565 of Apr. 5, 1990, titled “Sensor and Method for Measuring Alcohol Concentration in Alcohol-Gasoline Mixture” is related to a sensor and a method to measure mixtures of alcohol-gasoline mixtures for vehicular applications. The sensor delivers the information about the percentile of mixture to the injection system control, allowing the adjustment of fuel-air ratio. The method is based on the use of two different wavelengths, being one of then highly absorbed by alcohol and weakly absorbed by gasoline, and the second equally absorbed by both liquids. While one of the filters is centered at 1550 nm and the other is centered at 1300 nm, although other wavelengths can be used, in the ranges of 1450-1650 nm and in the range of 1200-1400 nm. The light source is an incandescent lamp working below its nominal voltage. The detectors are based on thermocouples suited to operate in the appropriate ranges. This system also comprises filters, to select the specific wavelength ranges, and the necessary electronics to amplify and further process the signals.
European patent EP0494734B1, of Aug. 5, 1998, titled “A method and Apparatus for Determining the Composition of a Fuel Mixture” is related to a method to determine the composition of a fuel mixture as well as the equipment used measure it. This patent is related to the measurement of the mixture o alcohols (ethanol and methanol) with gasoline, as well as the percentile of the many compounds that constitute gasoline. The method consists of absorbance measurement in the near infrared (NIR—between 650 and 2500 nm), more specifically to the stretching motion of the C—H bond located between 2000 and 2500 nm, 1700 and 1800 nm and a small peak at 1200 nm, as well as the stretching of the O—H bond observed between 1400 and 1650 nm. The method uses a double beam for emulsification detection which can happen in alcohol gasoline mixtures. The apparatus is designed to be used embarked allowing the vehicle ignition system to know which proportion of mixture is being injected in the pistons, and therefore allowing adjust the performance of the engine. The apparatus uses a light source which emits radiation in the near infrared range. The light detection is performed using InGaAs detectors which operate in de referred range. Interference filters are used to select the appropriate wavelengths. The apparatus also uses a diode located within the measurement chamber to measure temperature allowing appropriate corrections in the measurements.